The invention relates to a brake disc having ribs, which ribs are arranged between two friction rings, extend essentially in the radial direction and bound air cooling ducts by way of their side walls extending essentially perpendicular with respect to the surface of the friction rings. With respect to the technical background, reference is made, for example, to European Patent Document EP 1 048 872 B1 and also to German Patent Document DE 195 37 392 A1.
On the one hand, the cooling or the removal of the heat generated during a braking operation represents a significant challenge on brake discs, particularly on double-walled brake disc. For this purpose, a plurality of embodiments are known in which advantageously extending cooling air ducts between the two friction rings of a double-wall brake disc are formed or bounded by means of ribs, ribs, or the like. These ribs with their side walls bounding the cooling air ducts normally stand perpendicularly on the surface of the friction rings, as also illustrated in the above-mentioned European Patent Document EP 1 048 872 B1; furthermore, it is known to arrange the ribs in a framework-type manner inclined at an angle, for example, by an order of 45° with respect to the surfaces of the friction rings; compare, for example, German Patent Document 195 37 392 A1 also mentioned above.
Another problem may relate to vibrations of the rotating brake disc, particularly when, as a result of these vibrations, other components at least partially coming in contact with the brake disc are, in turn, stimulated to carry out vibrations which may then cause undesirable noise. The two above-mentioned prior art references also describe such noise and vibration problems. In this case, it is suggested in European Patent Document EP 1 048 872 B1 that the vibratory “brake disc” system or its natural frequency profile be detuned such that several slots extending in the radial direction are placed in a friction ring. In German Patent Document DE 195 37 392 A1, the ribs arranged in an inclined fashion in a framework-type manner are reinforced in the tangential direction.
It is an object of the invention to provide an effective measure for a vibration-related modification of the vibratory “brake disc” system for a brake disc having ribs arranged between two friction rings and extending essentially in the radial direction and bounding air cooling ducts by their side walls, which brake disc has basically been successful with respect to cooling problems. It must be possible to avoid with this measure the disadvantage of a mechanical weakening of the brake disc that is contained in the above-mentioned European Patent Document EP 1 048 872 B1, which occurs in this known state of the art because of the slots in the friction ring suggested there.
This and other objects are achieved by a brake disc having ribs arranged between two friction rings and extending essentially in the radial direction and bounding air cooling ducts by their side walls which stand essentially perpendicular with respect to the surface of the friction rings. At least one of the side walls of one, two, three or five ribs is inclined with respect to the perpendicularly standing ribs. For purposes herein, the term “ribs” is used generally to mean ribs, fins, slats, dividers, etc.
Advantageous further developments of the invention are described herein.
In order to achieve the desired goal of avoiding noise generating vibrations of a brake disc, particularly squealing noise, it was disclosed that only a relatively small system modification could achieve such a result. The slight vibration-related modification is achieved when only one or a few of the ribs have at least one inclined side wall, whereby, when the thickness of the rib (measured perpendicularly to the side walls) is not reduced, the rigidity of the “brake disc” system is significantly increased. This increase in rigidity can already be determined when only one or a few ribs are either inclined themselves—which means that their two side walls stand mutually parallel diagonally with respect to the surface of the friction rings and not perpendicularly on the surface of the friction rings—or when only one of the two side walls of one or a few ribs are inclined with respect to the adjacent perpendicularly standing ribs. In this case, the rib is inclined on one side.
Furthermore, it was described that better results are achieved by using the number of ribs disclosed here, i.e., one, two, three or five rib(s) inclined with respect to the plurality of perpendicular (with respect to the friction rings) ribs, or of ribs having at least one inclined side wall, on brake discs for passenger cars, which therefore have dimensions of a defined order of magnitude, and a total number of ribs also of a defined order of magnitude (in the range of from 40 to 60 ribs). In contrast, the use of four or six inclined ribs does not generate sufficient modification of the vibratory “brake disc” system either in the case of an essentially regular distribution over the surface of the friction rings, or in the case of their significant non-uniform distribution, unacceptably high imbalances are generated in the brake disc which can no longer easily be compensated.
Advantageously, a brake disc according to the invention having a few inclined ribs or having a few ribs with at least one inclined side wall is distinguished by lower weight and lower manufacturing costs from the above-mentioned state of the art according to which all ribs are arranged in a framework-type inclined manner (compare German Patent Document DE 195 37 392 A1).
In the case of at least one of the ribs having at least one inclined side wall, the rib thickness measured in the direction perpendicular to the side wall may differ from the thickness of the perpendicularly standing ribs, in which case the inclined rib or the inclined ribs may either be constructed to be thicker than the perpendicularly standing ribs—which results in a more intensive vibration-related modification of the vibratory “brake disc” system—or may be constructed to be slightly thinner than the perpendicularly standing ribs. In the last-mentioned case, the design can be such that the mass of an inclined rib, whose surface is naturally larger than that of a perpendicular rib, is essentially equal to the mass of the perpendicular rib, so that no significant imbalance of the brake disc is caused as a result of one inclined rib of this type or of a few of such inclined ribs.
The vibratory “brake disc” system can be modified particularly effectively with respect to conceivable stimulations of vibrations if, in the case of two or three or five ribs, of which at least one side wall is inclined with respect to the perpendicularly standing ribs, the angles enclosed between these inclined ribs (with an inclined wide wall) are not all the same. The corresponding inclined ribs are therefore arranged to be irregularly distributed over the surface of the friction rings. An imbalance resulting from such a non-uniform distribution of ribs with an inclined side wall can essentially be eliminated by the accumulation of material, particularly on appropriately selected perpendicularly standing ribs, which preferably are situated opposite the inclined ribs with respect to the brake disc center.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.